MTW-type zeolite and its preparation process

ABSTRACT

The invention relates to a synthetic crystalline zeolite of the MTW type, characterized by: 
     a) the following approximate general formula: 
     
         M.sub.2/n O, Al.sub.2 O.sub.3, xSiO.sub.2 
    
      in which M represents a metal cation and/or proton, n is the valency of M and x is a number between 14 and 800, 
     b) a X-ray diagram shown in table I of the description, 
     c) a fluorine content between approximately 0.005 and 2% by weight, said zeolite having been synthesized in a fluoride medium and accompanied by stirring.

The invention relates to a novel MTW-type zeolite and to a process forpreparing said zeolite.

Due to their geometrical selectivity and ion exchange properties,zeolites are industrially used on a considerable scale, both inadsorption (e.g. drying gases, separating straight and branched-chainparaffins, separation of aromatic compounds, etc.) and in catalysis(e.g. catalytic cracking, hydrocracking, isomerization, oligomerization,etc.).

The chemical composition of the zeolites containing in their skeletonthe elements Si and Al can be represented by the following approximateformula:

    M.sub.2/n, Al.sub.2 O.sub.3, xSiO.sub.2

in which

M represents a cation of valency n, such as e.g. an alkali metal,alkaline earth or organic cation,

x varying as a function of the structures between 2 and infinity and inwhich case the zeolite is a microporous silica.

Although numerous aluminosilicate-type zeolites exist naturally, thesearch for products having novel properties has led over the last fewyears to the synthesis of a large number of such zeolitic structurealuminosilicates. A novel zeolite, without any known natural equivalentand discovered in the early 1970's is the ZSM-12 zeolite (U.S. Pat. No.3,832,449). This zeolite is also known under the names CZH-5(GB-A-2079735), Nu-13 (EP-A-0059059), Theta-3 (EP-A-0162719) and TPZ-12(U.S. Pat. No. 4,557,919). The zeolite structure carrying thesedifferent names is referred to as of the MTW structural type (R. B.LaPierre et al, Zeolites, 5, p. 346, 1985). These MTW-type zeolites arestill synthesized in the presence of sodium cations and a very limitednumber of organic structuring agents. To obtain the MTW zeolite, it isnecessary to start with a reaction mixture containing Na⁺ cations and anorganic structuring agent, which can e.g. result from the reaction oftriethyl amine and diethyl sulphate.

All MTW-type zeolites have hitherto been synthesized in a conventionalmedium, i.e. in an alkaline medium at a pH generally exceeding 9, inwhich the silica mobilizing agent is OH⁻. Another zeolite synthesismedium has recently been discovered and is in fact the fluoride medium,in which the silica mobilizing agent is the F⁻ anion. In this medium,the pH is generally below 10 (cf. e.g. J. L. GUTH, H. KESSLER and R.WEY, Proc. Int. Zeolite Conf., Tokyo, Aug. 17-22, 1986, p. 121). Thesynthesis of a limited number of zeolytic structures has alreadysuccessfully taken place in this novel medium, such as e.g. MFI (Frenchpatent application 88/09631) and ferrierite (French patent application86/16362).

Compared with the alkaline synthesis medium (OH⁻), the fluoride mediumhas a certain number of very significant advantages. Thus, in analkaline medium, most synthesized zeolites are metastable. Thus, duringsynthesis more stable solid phases may appear and undesired phases areprecipitated. This difficulty increases when the quantities to beprepared increase, i.e. on passing from the laboratory to the industrialstage. Moreover, these metastable zeolites in the basic reaction mediumare only obtained by a significant supersaturation of active species inthe medium, which leads to a rapid nucleation and consequently tocrystals of approximately 1 micrometer. However, in certainapplications, it may be of interest to have crystals of a larger size,so as to e.g. maintain the thermal stability of the solid.

Numerous applications, particularly in acid catalysis, require zeolitesin a proton form completely free from their alkali metal or alkalineearth compensation cations introduced during synthesis. It is possibleto obtain the proton form by carrying out repeated, long exchanges withNH₄ ⁺ cations, followed by calcination in order to decompose the saidcations into protons. These ion exchange stages could be avoided if itwas possible to entirely replace the alkali metal or alkaline earthcations by cations decomposable during synthesis, i.e. NH₄ ⁺ and/ororganic cations. It is not possible to introduce NH₄ ⁺ cations into thesolid during synthesis in the basic medium because the pH is too highand then NH₄ ⁺ would be transformed into NH₃. In addition, synthesescarried out at pH-values where the NH₄ ⁺ cation is stable are difficultand long due to the limited solubility of the silica sources at theselow pH-values.

A supplementary advantage of syntheses carried out in a fluoride mediumcompared with those carried out in a conventional OH⁻ medium is thatsolids are obtained, whose acid and ion exchange properties are ofdifferent natures. The acid catalysts prepared from solids obtained inthe fluoride medium have improved catalytic properties. At this level itis very important to point out that the crystallographic structure of asolid is not sufficient for entirely defining its properties and moreparticularly its acid properties, which play a vital part in catalysis.

Unlike in the case of their homologs prepared according to the priorart, the MTW-type zeolites prepared according to the invention containfluorine after the synthesis and elimination of the organic compoundsintroduced during synthesis. Fluorine, as will be shown hereinafter,gives the MTW zeolites according to the invention special acid and ionexchange properties. Another important advantage of the fluoridesynthesis medium is it makes it possible to obtain sodium cation-freeMTW zeolites.

The invention therefore relates to a novel, synthetic, crystallineMTW-type zeolite, as well as to a process for the synthesis of saidzeolite in which the aforementioned disadvantages are avoided and whichalso gives to the zeolites according to the invention improvedproperties and in particular acid properties. The novel zeolite typeaccording to the invention can be used in adsorption and in catalysis.The MTW-type zeolite according to the invention has (after synthesis)the following approximate general formula:

    M.sub.2/n, Al.sub.2 O.sub.3, xSiO.sub.2

in which M represents a proton and/or a metal cation (n being thevalency of M).

It will be shown hereinafter that in a preparation method according tothe invention, said metal cation or proton results from the thermaldecomposition of at least one cation such as e.g. NH₄ ⁺ and/or at leastone organic agent such as methyl amine (CH₃ NH₂) or1,4-diazabicyclo-(2,2,2)-octane (hereinafter called DABCO) present inthe reaction medium and/or at least one non-decomposable metal cationwhich may or may not have come from the reaction medium such as e.g. analkali metal and/or alkaline earth cation or some other metal cationdefined hereinafter.

The zeolite according to the invention is in particular characterizedby:

i) a number x between 14 and 800, preferably between 20 and 800 (x beingthe SiO₂ /Al₂ O₃ molar ratio),

ii) a X-ray diagram shown in table I,

iii) a fluorine content between approximately 0.005 and 2% by weight,preferably between approximately 0.01 and 1.5% by weight.

It is also characterized by the fact that it was synthesized in afluoride medium and in a stirred medium.

This MTW-type zeolite according to the invention generally has at leastone dimension of the crystals between 0.1 and 50 μm (1 μm=10⁻⁶ meter).

The invention also relates to a process for the preparation of saidMTW-type zeolite, which consists:

a) of forming a reaction mixture in solution having a pH belowapproximately 9 and containing water, at least one silica source, atleast one aluminium source, at least one mobilizing agent sourcecontaining fluoride (F⁻) ions, at least one source of at least onestructuring agent chosen from within the group formed by1,4-diazabicyclo-(2,2,2)-octane and a mixture of1,4-diazabicyclo-(2,2,2)-octane and methyl amine, said structuring agentpossibly supplying organic cations, optionally an alkali metal and/oralkaline earth cation source, said reaction mixture having acomposition, in molar ratio terms, within the following ranges:

Si/Al: 6-300, preferably 10-300,

F⁻ /Si: 0.1-8, preferably 0.2-6,

H₂ O/Si: 4-50, preferably 10-50,

(R+R')/Si: 0.5-4,

R/R': 0.1-infinity, preferably 0.2-infinity, in which R is DABCO and R'methyl amine (R'=0 in the case where methyl amine is not used).

b) maintaining said reaction mixture under stirring at a heatingtemperature between approximately 100° and 250° C. and preferablybetween approximately 150° and 250° C. until a crystalline compound isobtained and

c) calcining said compound at a temperature above approximately 350° C.and preferably above approximately 450° C.

The presence, following the calcination stage (stage c)) for eliminatingthe organic compounds, of fluorine in said MTW-type zeolites accordingto the invention, at contents preferably between 0.01 and 1.5% by weightleads to modifications of the ion exchange and acid properties of thesolids, which are different from the MTW zeolites obtained in aconventional medium. Thus, as a function of the synthesis conditions,the solids according to the invention are characterized by an infraredvibration spectrum in the OH range (3800 to 3500 cm⁻¹) having bandsattributed to the Si-OH groups (range 3730-3750 cm⁻¹) and to the Al-OHgroups (range 3580-3640 cm⁻¹) which are less intense than those of theprior art MTW zeolites with the same Si/Al ratio. Correlatively the ionexchange capcity of the zeolites according to the invention is generallylower than that of the prior art products.

The MTW zeolites according to the invention, whose hydroxyl content andion exchange capacities are reduced, surprisingly have remarkable acidproperties as is witnessed by the ammonia thermodesorption and theinfrared spectroscopy of adsorbed weak bases such as e.g. ethylene andH₂ S. It is therefore clear that the acidity of the solids according tothe invention is of a special nature. Without wishing to be bound by aparticular theory, it can be suggested that in the solids according tothe invention a more or less large part of the acid sites of theskeleton of type Si-OH-Al is replaced by sites of the type Si-F-Al.

The exact nature of the acid sites contained in the MTW zeolitesaccording to the invention remains to be defined. However, it would seemthat the existence of these special sites is linked with the presence offluorine in the solids or at least results from the fact that thesynthesis was carried out in a fluoride medium.

By special treatments it would be possible to eliminate all or part ofthe fluorine contained in the solids according to the invention withoutcausing any deterioration to their crystallinity. One procedure whichcan be used for defluorinating said solids consists of carrying out atreatment in a NH₄ OH solution at temperatures e.g. between ambienttemperature (15° to 25° C.) and 150° C. (treatment under pressure).

It is advantageously possible to heat the reaction medium in anautoclave internally coated with polytetrafluoroethylene (PTFE) betweenapproximately 100 and approximately 250° C. and preferably betweenapproximately 150 and approximately 250° C. for a time which can varyfrom a few hours to a few days (normally between 8 and 1200 hours), as afunction of the reaction temperature adopted, until a crystalline solidis obtained which is separated from the mother liquors by filtration andwhich is then washed with distilled water. The reaction mixture must bestirred during the heating period in the autoclave in order to obtainthe MTW-type solid according to the invention.

Advantageously, it is possible to prepare said reaction mixture at a pHbetween approximately 4 and approximately 9 and preferably betweenapproximately 6 and approximately 9.

According to a preferred method for the preparation of MTW-type zeolitesaccording to the invention, the molar ratios of the constituents of thereaction mixture are within the following value ranges:

Si/Al: 12-100,

F⁻ /Si: 0.5-4,

H₂ O/Si: 20-40

(R+R')/Si: 0.9-2.1,

R/R': 0.3-infinity, in which R is DABCO and R' is methyl amine (R'=0 inthe case where methyl amine is not used).

It is optionally possible to add to said reaction mixture at least onecomplementary salt in a complementary salt/SiO₂ molar ratio generallybetween 0.1 and 4 and preferably between 0.2 and 0.5 and/or at least onenucleus of the zeolite formed according to the invention in a zeolitecrystal/SiO₂ weight ratio generally between 0.01 and 0.1 and preferablybetween 0.02 and 0.03, in such a way that the morphology, the size ofthe crystals and the crystallization reaction kinetics can beadvantageously controlled.

The pH of the reaction medium, below approximately 9, can be obtainedeither directly from one or more of the reagents used, or by theaddition of an acid, a base, an acid salt, a basic salt or acomplementary buffer mixture.

Numerous silica sources can be used. Reference is made to silicas in theform of hydrogels, aerogels and colloidal suspensions, as well assilicas resulting from the precipitation of solutions of solublesilicates or the hydrolysis of silicic esters such as orthosilicic acidtetraethyl ester (Si(OC₂ H₅) or complexes such as sodium fluorosilicateNa₂ SiF₆ or ammonium fluorisilicate (NH₄)₂ SiF₆.

Among the aluminium sources used, preference is given to the choice ofaluminium chloride hydrate (AlCl₃, 6H₂ O), aluminium nitrate hydrate(Al(NO₃)₃, 9H₂ O), aluminium sulphate with 16 molecules of water oraluminium fluoride trihydrate AlF₃, 3H₂ O. Reference can also be made topseudoboehmite.

Moreover, instead of starting with separate silica and aluminiumsources, it is also possible to use sources where the two elements arecombined, such as e.g. a freshly precipitated aluminosilicate gel.

The fluoride anions F⁻ can be introduced in the form of salts of saidstructuring agents or ammonium or alkali metals such as e.g. NaF, NH₄ F,NH₄ HF₂ or in acid form such as HF, or in the form of hydrolyzablecompounds able to release fluoride anions in water such as siliconfluoride SiF₄ or ammonium fluorosilicate (NH₄)₂ SiF₆ or sodiumfluorosilicate Na₂ SiF₆.

The acids or acid bases, bases or basic salts optionally added forbringing the pH of the reaction medium to the desired value can bechosen from among standard acids such as e.g. HF, HCl, HNO₃, H₂ SO₄, CH₃COOH or acid salts such as e.g. NH₄ HF₂, KHF₂, NaHSO₄, standard basessuch as e.g. NaHCO₃, Na₂ S, NaHS or buffer mixtures such as e.g. (CH₃COOH, CH₃ COONa) or (NH₄ OH, NH₄ Cl).

Calcination (stage c) advantageously takes place at a temperaturebetween approximately 520° and 800° C. in a dry gas atmosphere, such ase.g. air or inert gas, so as to decompose the structuring agent presentin the pores of the zeolite.

Following the stage of eliminating the organic compound (stage c) andoptionally partial or total defluorination, it is possible to introduceinto the MTW-type zeolite according to the invention and using wellknown ion exchange methods, at least one element from the periodicclassification, whose cations can be prepared in an aqueous medium andchosen from within the family constituted by groups IIA, IIIA, IB, IIB,IIIB, IVB and VIIIA of the period classification of elements. Referenceis e.g. made to alkali metal, alkaline earth or rare earth cations Fe",Fe'", Co", Co'", Ni", Cu", Zn", Ag', Pt".

The identification of the MTW-type zeolites according to the inventioncan take place easily on the basis of their X-ray diagram, which can beobtained with the aid of a diffractometer using the conventional powdermethod with Kα radiation of the copper. An internal standard makes itpossible to accurately determine the values of the angles 2θ associatedwith the diffraction peaks. The different interplanar spacings d_(hkl)characteristic of the sample are calculated on the basis of Bragg's law.The estimation of the measuring errors Δd_(hkl) on d_(hkl) is calculatedas a function of the absolute error Δ(2θ) allocated to the measurementof 2θ by Bragg's law. In the presence of an internal standard, thiserror is minimized and is taken as equal to ±0.05°. The relativeintensity l/lo allocated to each value of d_(hkl) is estimated on thebasis of the height of the corresponding diffraction peak. The lattercan also be determined on the basis of a radiograph obtained with theaid of a powder camera.

Table I shows the X-ray diagram of the MTW-type zeolites according tothe invention. The values relate to Kα radiation copper (λ=1.5418 Å),the data having been obtained with the aid of an automatic PhillipsAPD1700 Diffractometer (Line Fine Focus tube). The MTW zeolite accordingto the invention can be used alone or mixed with a matrix within acatalyst.

After synthesis, the zeolite can e.g. be shaped using a matrix, whichmay be inert or active for the reaction to be promoted. The matrixesused are generally chosen from within the group formed by clays,aluminas, silica, magnesia, zirconia, titanium dioxide, boron trioxideand any combination of at least two of the above compounds such assilica-alumina, silica-magnesia, etc. All known agglomeration andshaping methods can be used, such as e.g. extrusion, pelletizing, dropcoagulation, etc.

The catalyst then has a weight content of the MTW-type zeolite accordingto the invention generally between 20 and 99.5%, preferably between 40and 95% and a matrix weight content generally between 0.5 and 80% andpreferably between 5 and 60%.

The catalyst containing the MTW structure zeolite according to theinvention can also contain a hydrogenating or dehydrogenating functionconstituted in general by at least one metal and/or metal compoundchosen from among groups IA, VIB (Cr, Mo, W) and VIII of the periodicclassification of elements, e.g. platinum, palladium and/or nickel.

                  TABLE I                                                         ______________________________________                                        2θ(°)                                                                     I/Io           2θ(°)                                                                   I/Io                                           ______________________________________                                        7.45     82             26.37  13                                             7.66     56             26.89  12                                             8.88     30             28.02  9                                              12.15     2             28.51  3                                              14.79     5             29.35  5                                              15.28     6             30.98  6                                              18.76    10             31.79  2                                              19.14    11             32.89  1                                              20.05     7             33.83  3                                              20.91    100            35.68  14                                             21.91     8             36.51  2                                              22.43    15             36.99  3                                              23.05    39             38.49  2                                              23.31    28             43.84  1                                              23.88     5             44.64  4                                              24.52     4             45.64  2                                              25.20     6             46.88  2                                              25.77     7                                                                   ______________________________________                                    

The following examples illustrate the invention without limiting itsscope.

EXAMPLE 1

3.37 g of DABCO (0.03 mole) and 2.33 g of aqueous solution with 40%methyl amine (0.03 mole of methyl amine) are dissolved in 17.7 g ofwater. To this solution are added dropwise and accompanied by stirring 3g of an aqueous solution with 40% HF (0.06 mole of HF). To the mixtureobtained is added accompanied by stirring 0.14 g of pseudoboehmite with24.6% by weight water (i.e. 2·10⁻³ mole of Al) and 4.23 g of Mercksilica with 15% water (i.e. 0.06 mole of SiO₂) and finally approximately70 mg of MTW-type zeolite crystals synthesized in a carefully groundfluoride medium (approximately 2% by weight based on the silica used).This reaction mixture is stirred for 10 minutes at ambient temperature.

The composition of the reaction mixture in molar ratio terms is asfollows:

Si/Al=30; F⁻ /Si=1; (R+R')/Si=1; R/R'=1 and H₂ O/Si=20

The reaction mixture is then transferred into a TEFLON-coated 75 mlautoclave, the reaction taking place at 200° C. for 24 hours. Duringsynthesis, the autoclave is continuously stirred, the longitudinal shaftof the autoclave rotating at a speed of approximately 15 revolutions perminute (r.p.m.) in a plane perpendicular to the rotation axis. After thereaction, the autoclave is cooled, the crystalline solid is collected byfiltration, washed with distilled water and dried at 80° C. for 24hours. The pH of the reaction medium before and after the reaction isapproximately 8.

The X-ray diffraction spectrum of the collected product is similar,after calcination in air at 550° C., to that of table I of thedescription (MTW-type structure). Examined under the electron scanningmicroscope, said zeolite is in the form of fine interlaced needles ofaverage dimensions 5×0.2 μm. The SiO₂ /Al₂ O₃ molar ratio of the solidobtained is 126, the fluorine weight content, after calcination in airat 550° C., being 0.5%.

EXAMPLE 2

A reaction mixture having an identical composition to that of example 1is transferred into a TEFLON-coated 75 ml autoclave. The autoclave isheated to 170° C. for 12 days under the same stirring conditions as inexample 1. The collected, washed and dried solid has, after calcinationin air at 550° C., a X-ray diagram identical to that of table I. ItsSiO₂ /Al₂ O₃ molar ratio is equal to 90, its fluorine weight contentafter calcination in air at 50° C. being 0.25%.

EXAMPLE 3

A reaction mixture, whose molar composition is given hereinafter, isprepared according to an operating procedure identical to that ofexample 1. The quantities of the reagents used are the same, except withregards to the pseudoboehmite which is in this case 40 mg (i.e. 6·10⁻⁴mole of Al) instead of 0.14 g. The molar composition of the reactionmixture is then as follows:

Si/Al=100; F⁻ /Si=1; (R+R')/Si=1; R/R'=1; H₂ O/Si=20

After transfer into a TEFLON-coated 75ml autoclave, the reaction mixtureis heated to 170° C. for 5 days and accompanied by stirring. Afterreaction, the solid obtained is collected by filtration, washed withdistilled water and dried. After calcination in air at 550° C., it has aX-ray diagram identical to that of table I. Its SiO₂ /Al₂ O₃ molar ratiois 200 and after calcining in air at 550° C., its fluorine weightcontent is 0.7%.

EXAMPLE 4

3.37 g of DABCO (0.03 mole) and 2.32 g of aqueous solution with 40%methyl amine (0.03mole of methyl amine) are dissolved in 18.4 g ofwater. To this solution are added dropwise and accompanied by stirring 3g of an aqueous solution with 40% HF (0.06 mole of HF). To the mixtureobtained are added, accompanied by stirring, 83 mg of AlF₃,3H₂ O (0.01mole of Al) and 4.23 g of Merck silica with 15% water (i.e. 0.06 mole ofSiO₂) and finally approximately 70 mg of MTW-type zeolite crystalssynthesized in a carefully ground fluoride medium (approximately 2% byweight based on the silica used). This reaction mixture is stirred for10 minutes at ambient temperature. The composition of the reactionmixture in molar ratio terms is as follows:

Si/Al=6; F⁻ /Si=1.5; (R+R')/Si=1; R/R'=1 and H₂ O/Si=20

The reaction mixture is then transferred into a TEFLON-coated 75 mlautoclave, the reaction taking place at 200° C. for 2 days. Duringsynthesis, the autoclave is continuously stirred, the longitudinal shaftof the autoclave rotating at a speed of approximately 15 r.p.m. in aplane perpendicular to the rotation axis. After reaction, the autoclaveis cooled, the crystalline solid collected by filtration, washed withdistilled water and dried at 80° C. for 24 hours. The pH of the reactionmedium before and after the reaction is approximately 8.

The X-ray difference spectrum of the collected product is, aftercalcining in air at 550° C., similar to that of table I (MTW-typestructure). Examined under the electron scanning microscope the zeoliteis in the form of fine interlaced needles of length 20 to 30 μm. TheSiO₂ /Al₂ O₃ molar ratio of the solid is close to 38, its fluorineweight content after calcining in air at 550° C. being 0.55%.

We claim:
 1. Synthetic crystalline zeolite of the MTW type characterizedby:a) the following approximate general formula:

    M.sub.2/n O, Al.sub.2 O.sub.3, xSiO.sub.2

in which M represents a metal cation and/or a proton, n is the valencyof M and x is a number between 14 and 800, b) a X-ray diagram shown intable I of the description, c) a fluorine content between approximately0.005 and 2% by weight, said zeolite having been synthesized in afluoride medium, accompanied by stirring.
 2. Zeolite according to claim1, characterized in that x is a number between 20 and
 800. 3. Zeoliteaccording to either of the claims 1 and 2, characterized in that it hasa fluorine content between approximately 0.01 and 1.5% by weight. 4.Catalyst containing a zeolite according to claim 1 wherein said catalystfurther comprises a matrix.
 5. Catalyst containing a zeolite accordingto claim 1 wherein said catalyst further comprises a matrix at least onemetal and/or metal compound chosen from among groups IA, VIB and VIII ofthe periodic classification of elements.
 6. Process for the preparationof a zeolite according to claim 1, characterized in that:a) a reactionmixture in solution is formed having a pH below approximately 9 andcontaining water, at least one silica source, at least one aluminiumsource, at least one mobilizing agent source containing fluoride ions(F⁻), at least one source of at least one structuring agent chosen fromwithin the group formed by 1,4-diazabicyclo-(2,2,2)-octane and a mixtureof 1,4-diazabicyclo-(2,2,2)-octane and methyl amine, said structuringagent optionally supplying organic cations, said reaction mixture havinga composition, in molar ratio terms, within the following valueranges:Si/Al: 6-300, F⁻ /Si: 0.1-8, H₂ O/Si: 4-50, (R+R')/Si: 0.5-4,R/R': 0.1-infinity, in which R is 1,4-diazabicyclo-(2,2,2)-octane and R'is methyl amine. b) the said reaction mixture is maintained understirring at a heating temperature between approximately 100° and 250° C.until a crystalline compound is obtained and c) said compound iscalcined at a temperature above approximately 350° C.
 7. Processaccording to claim 6, wherein, in stage a), the reaction mixture has acomposition, in molar ratio terms, within the following valueranges:Si/Al:10-300, F⁻ /Si:0.2-6, H₂ O/Si:10-50, (R+R')/Si:0.5-4,R/R':0.2-infinity, in which R is 1,4-diazabicyclo-(2,2,2)-octane and R'is methyl amine.
 8. Process according to claim 6, wherein, in stage a),said reaction mixture has a composition, in molar ratio terms, withinthe following value ranges:Si/Al:12-100 F⁻ /Si:0.5-4, H₂ O/Si:20-40,(R+R')/Si:0.9-2.1, R/R':0.3-infinity in which R is1,4-diazabicyclo-(2,2,2)-octane and R' is methyl amine.
 9. Processaccording to any one of the claims 6 to 8, wherein, in stage a), saidreaction mixture also incorporates an alkali metal and/or alkaline earthcation source.
 10. Process according to claim 9, wherein, in stage b),said reaction mixture is maintained at a heating temperature betweenapproximately 150° and 250° C., the reaction mixture being kept understirring until a crystalline compound is obtained.